Foundation or anchor bolts (hereinafter “foundation bolts”) are conventionally used to secure large structures such as wind turbine or utility towers to their respective foundation. Typically, foundation bolts are secured and/or anchored into the foundation block or slab, generally consisting of concrete or other similar materials.
To provide a more secure engagement between the towers and their respective foundation, the foundation bolts used in mounting these large towers are typically tensioned.
In certain prior art tensioning systems, foundation bolts are tensioned using two or more hydraulic jacks temporarily mounted next to the bolt and coupled thereto by a generally rigid plate mounted to the bolt. The jacks are then actuated and the upward force generated thereby is transmitted to the bolt via the plate. The tension in the bolt is then maintained by threading down the foundation nut until it abuts on the foundation surface.
Even though the aforementioned installation does provide adequate results, it remains cumbersome to handle and prone to accident. Indeed, the installation necessitates at least two hydraulic jacks, a rigid plate and an additional nut which must be properly installed before tensioning each bolt. Hence, the installation is time consuming. Additionally, variability in the installation of the jacks and variability in the forces generated thereby may affect the resulting tension in the bolt and may ultimately damage the rigid plate, the bolt or even both. Finally, since the tensioning installation is seldom perfectly symmetrical, one of the jacks may disengage itself from the rigid plate, resulting in damages to the installation and to the bolt and possibly even injuries to the operator.
Conventional tensioners are also sometimes used to tension foundation bolts. Still, conventional tensioners have problems of their own.
Firstly, conventional tensioners are not particularly adapted to be used on foundation bolts due to the length of the latter. Indeed, to tension a foundation bolt using a conventional tensioner, the tensioner must first be installed and then the reaction nut which transmits the upward force to the bolt must be manually threaded down all the way along the length of the bolt. Understandably, this manual threading is particularly time consuming, the more so when dozens of foundation bolts must be tensioned for each turbine or tower.
Secondly, due to the length of foundation bolts, the latter are prone to being damaged, either by bending the bolt or by damaging the threads thereon. To tension a damaged bolt using a conventional tension can become problematic since it is sometimes difficult or even impossible to thread the reaction nut along the damaged portion of the bolt.
Consequently, using prior art tensioning systems and tensioners to tension foundation bolts is particularly time consuming, prone to accidents and sometimes even impossible. Hence, a need still exists for a novel foundation bolt tensioner which will mitigate the aforementioned and other shortcomings of the prior art.